The present invention has, as its aim, a device for the pneumatic splicing of threads or yarns.
Furthermore, the present invention has, as its aim, a process for the pneumatic splicing of threads or yarns. Compressed air devices for splicing textile yarns are known, commonly referred to as air splicers. The qualitative result of the compressed air splicing of threads is defined by tensile stress resistance and appearance, both comparable to the corresponding thread.
It is clear that the closer the similarity of resistance and appearance to the corresponding thread, the better the splice.
In particular, the known splicing devices have guides to assist the introduction of the threads, clamping and cutting members for the same threads, preparation members for the thread ends, withdrawal members for the cut threads in the direction of the splice box, and a splice box made in a casing and equipped with a through lengthwise slot for the introduction and extraction of threads, in which emerge one or more compressed air feed holes or nozzles.
The splice box also has lateral outlet edges for the discharge of pressurized air.
The following is a typical operating sequence for devices of this kind: introduction into the device of the thread ends to be spliced, the clamping and cutting of threads, opening of the thread ends using compressed air to remove the twist, withdrawal of the ends in the direction of the box.
At this point, one or more blasts of compressed air are introduced into the splice box to carry out the proper splicing.
Lastly, the spliced thread is released and all the members return to their initial position.
In the above defined splice box, the presence of one or more entry nozzles and the shape of the box itself allow the compressed air to be appropriately directed to perform the splice.
Considering, in more detail, the action of the compressed air on the thread fibres to be spliced, it is noted that this performs an interweaving or mixing action and a winding action of the fibres with each other.
These two effects are basically present simultaneously in the majority of box shapes used. However, depending on the box sections and the position of the jet nozzles, either the interweaving or the winding action may be prevalent.
For a better understanding of the phenomenon described it should be noted that, for splice quality the greater the interweaving or joining effect and resistance to tensile stress, the greater is the winding effect and the better is the appearance of the splice itself.
Moreover, there are yarns which have a propensity for greater interweaving (usually tough, long fibre yarns) and yarns which have a propensity for more winding (usually short fibre yarns, also known as cotton cut).
It has been found that a different position of the jet nozzles can be used, in the same box section, to obtain both the interweaving as well as the winding effect.
Therefore a patent application has been filed which puts the above principle into practice, by using two different ducts to transport the air to different nozzles and with two blasts of compressed air at successive times (one for each duct).
A more effective variant, described in the patent IT 1.251.856, envisages a double sectioned box: a central V-shaped section helps mixing, into which a nozzle emerges with a special duct and a circular type section at the two ends, with two suitably directed nozzles, one at each end, with their shared duct, to help the winding of the fibres with each other.
Air flow in the two ducts is started at different, subsequent moments.
The practical effect is the possibility to use the same box for different yarn types and therefore make the device more suitable for industrial use, without having to replace any parts (the splice box) in order to be able to splice different yarn types.
Nevertheless, both the suggested solutions, which are mentioned above, though valid, are the result of a compromise between sections and/or feed nozzles of compressed air in the box and have not produced wholly satisfactory results on a large number of textile yarns.
Therefore, the aim of the present invention is to produce a device for the pneumatic splicing of threads or yarns which produces excellent resistance and a splice which is very similar in appearance to that of the reference yarn and so for a greater number of yarn types, compared to previous suggested solutions.
Another aim of the present invention is to produce a splicing device which can save a considerable amount of time, eliminating unnecessary machine stops for the replacement of the splice box.
Another aim of the present invention is to produce a simple and economic splicing device.
These and other aims are reached by a device for pneumatic splicing of threads or yarns, including one splice box, equipped with lateral outlet edges and with an upper lengthwise slot, through which thread ends are introduced into said splice box and through which it is possible to blow in pressurized air into said splice box, further comprising means to open and close, at least partially, said lateral outlet edges so as to be able to carry out an initial introduction of at least one blast of compressed air into said splice box when said lateral outlet edges are mostly closed, and a second introduction of at least one blast of air into said splice box when the lateral outlet edges are mostly or completely open.
Moreover, such aims are reached by a process for pneumatic splicing of threads or yarns, including, in sequence, at least the following stages: the introduction into a splice box, belonging to a splicing device, of said thread ends to be spliced together; clamping and cutting of said threads; detwisting and opening of thread ends using compressed air and withdrawal of the ends in the direction of the splice box; an initial introduction of at least one blast of compressed air into said splice box when it is mostly closed at its lateral outlet edges, in order to help mixing; the opening of the lateral outlet edges; a second introduction of at least one blast of compressed air into said splice box when this is at least partially open at the lateral outlet edges, in order to help winding, release of the spliced thread and the return of all members to their original position.
In addition, further characteristics of the present invention are defined in the following claims.